Striking tool

ABSTRACT

A technique for improving the vibration-proof effect and usability of a handle is provided in an impact tool. An impact tool is provided which linearly drives a tool bit in an axial direction thereof to cause the tool bit to perform a predetermined hammering operation. The impact tool includes a motor, a striking mechanism part, that is driven by the motor and causes the tool bit to linearly move, a tool body that houses the motor and the striking mechanism part, an outer shell housing that covers at least part of the tool body and is connected to the tool body via a vibration-proofing first elastic element so as to be movable in a direction transverse to the axial direction of the tool bit with respect to the tool body, and a handle which is designed to be held by a user and connected to an opposite side of the outer shell housing from the tool bit via a vibration-proofing second elastic element so as to be movable in the axial direction of the tool bit with respect to the outer shell housing.

FIELD OF THE INVENTION

The present invention relates to a vibration-proofing technique in astriking impact tool.

BACKGROUND OF THE INVENTION

Japanese Patent No. 3520130 discloses an electric hammer in which ahousing integrally provided with a handle is connected to a strikingmechanism part for striking a hammer bit, via an elastic element.

During operation using an electric hammer, vibration is caused in astriking mechanism part of the hammer not only in an axial direction ofa tool bit in which the tool bit performs striking movement, but also ina direction transverse to the axial direction. Therefore, a technique isdesired which can prevent vibration in various directions.

DISCLOSURE OF THE INVENTION Object to be Achieved by the Invention

Accordingly, it is an object of the present invention to provide animpact tool in which the vibration-proof effect and usability of ahandle are further improved.

Means for Achieving the Object

In order to achieve the above-described object, according to a preferredembodiment of the present invention, an impact tool is provided whichlinearly drives a tool bit in an axial direction of the tool bit tocause the tool bit to perform a predetermined hammering operation. The“impact tool” in this invention is not limited to a hammer in which atool bit is caused to linearly move in the axial direction, and alsosuitably includes a hammer drill in which a tool bit is caused tolinearly move in the axial direction and rotate around its axis.

The impact tool according to this invention is characterized in that itincludes a motor, a striking mechanism part which is driven by the motorand causes the tool bit to linearly move, a tool body which houses themotor and the striking mechanism part, an outer shell housing whichcovers at least part of the tool body, a first elastic element whichelastically connects the outer shell housing to the tool body such thatthe outer shell housing can move in a direction transverse to the axialdirection of the tool bit with respect to the tool body, a handledesigned to be held by a user, and a second elastic element whichconnects the handle to the outer shell housing such that the handle canmove in the axial direction of the tool bit with respect to the toolbody.

The “striking mechanism part” in this invention typically includes amotion converting mechanism which converts torque of the motor intolinear motion, and a striker which is linearly driven via pressurefluctuations (air spring action) caused by this linear motion andstrikes the tool bit. Further, the “first elastic element” and the“second elastic element” in this invention represent a spring or rubber.

According to this invention, as for vibration caused in the tool bodythat houses the striking mechanism part which is a vibrating source,vibration in the axial direction (the striking direction) of the toolbit is reduced by the second elastic element which connects the outershell housing and the handle, while vibration in a direction transverseto the axial direction is reduced by the first elastic element whichconnects the tool body and the outer shell housing. Thus, byindividually setting stiffness (spring constant) of the first and secondelastic elements, the handle is made proof against vibration not only inthe axial direction but also in a direction transverse to the axialdirection. Furthermore, the handle can be prevented from wobbling in adirection transverse to the axial direction. Thus, usability of thehandle can be improved.

According to a further embodiment of the impact tool of the presentinvention, the handle has a grip region extending in a directiontransverse to the axial direction of the tool bit and one end of thegrip region in an extending direction is connected to the outer shellhousing by the second elastic element comprising a mechanical spring. Inthe case of an impact tool, the user holds the handle and performs anoperation while applying a pressing force to the handle in a directionto press the tool bit against a workpiece. Therefore, by provision ofthe construction like in the present invention in which the grip regionof the handle extends in a direction transverse to the axial directionof the tool bit, the operation of pressing the tool bit can be easilyperformed.

According to a further embodiment of the impact tool of the presentinvention, the outer shell housing is split into a plurality of splitelements in the axial direction of the tool bit and formed by connectingthe split elements to each other. According to this invention, when aplurality of split elements are clamped and connected together, forexample, by screws, the split elements can be easily assembled together,with the first elastic element held between the outer shell housing andthe tool body, so that ease of assembling the split elements isimproved.

According to a further embodiment of the impact tool of the presentinvention, the tool body has a cylindrical barrel extending in the axialdirection of the tool bit. Further, an O-ring is disposed between anouter circumferential surface of the barrel and an inner circumferentialsurface of the outer shell housing which covers the barrel, and the toolbody and the outer shell housing are positioned in a radial direction bythe O-ring. Further, the “radial direction” in this invention refers toa direction transverse to the axial direction of the tool bit.

According to this invention, the O-ring can serve as the first elasticelement which connects the outer shell housing to the tool body.

In order to solve the above-described problem, according to a differentembodiment of the present invention, an impact tool is provided whichlinearly drives a tool bit in an axial direction thereof to cause thetool bit to perform a predetermined hammering operation. Further, the“impact tool” in this invention is not limited to a hammer in which atool bit is caused to linearly move in the axial direction; and alsosuitably includes a hammer drill in which a tool bit is caused tolinearly move in the axial direction and rotate around its axis.

The impact tool according to this invention is characterized in that itincludes a motor, a striking mechanism part which is driven by the motorand causes the tool bit to linearly move, a tool body which houses themotor and the striking mechanism part, an outer shell housing whichcovers at least part of the tool body, and a handle which is designed tobe held by a user and integrally formed on an opposite side of the outershell housing from the tool bit. The outer shell housing is connected tothe tool body via at least a first elastic element which can elasticallydeform in a direction transverse to the axial direction of the tool bitand a second elastic element which can elastically deform in the axialdirection of the tool bit. Further, the “striking mechanism part” inthis invention typically includes a motion converting mechanism whichconverts torque of the motor into linear motion, and a striker which islinearly driven via pressure fluctuations (air spring action) caused bythe linear motion of the motion converting mechanism and strikes thetool bit. The manner of “being integrally formed” in this inventionsuitably includes the manner in which the outer shell housing and thehandle are integrally formed with each other or the manner in which theouter shell housing and the handle are separately formed and thereafterfixed to each other. Further, the “first elastic element” and the“second elastic element” in this invention represent a spring or rubber.

According to this invention, when the user holds the handle of theimpact tool and performs an operation, as for vibration which is causedin the striking mechanism part and transmitted to the outer shellhousing, vibration in the axial direction of the tool bit is preventedby the second elastic element, while vibration in a direction transverseto the axial direction of the tool bit is prevented by the first elasticelement. Therefore, by individually setting stiffness (spring constant)of the first and second elastic elements, the handle is made proofagainst vibration not only in the axial direction but also in adirection transverse to the axial direction. Furthermore, the handle canbe prevented from wobbling in a direction transverse to the axialdirection. Thus, usability of the handle can be improved.

According to a further embodiment of the impact tool of the presentinvention, in the impact tool in which the handle is integrally formedwith the outer shell housing, a rod-like member is provided in the toolbody and slidably extends through the tool body in the axial directionof the tool bit. The rod-like member serves as a guide rail for guidingmovement of the outer shell housing in the axial direction of the toolbit with respect to the tool body. With such a construction, movement ofthe outer shell housing in the axial direction of the tool bit withrespect to the tool body can be stabilized, so that usability of thehandle can be improved.

In a further embodiment of the impact tool of the present invention, therod-like member and the outer shell housing are connected to each othervia the first elastic element. Thus, a vibration-proofing structure forpreventing vibration of the outer shell housing and the handle in adirection transverse to the axial direction of the tool bit can berationally formed by the first elastic element.

In a further embodiment of the impact tool of the present invention, adynamic vibration reducer for reducing vibration of the outer shellhousing in the axial direction of the tool bit is provided in the outershell housing. According to this invention, vibration in the axialdirection of the tool bit which cannot be fully prevented by the secondelastic element can be further reduced by the vibration reducingfunction of the dynamic vibration reducer.

Effect of the Invention

According to this invention, a technique for improving thevibration-proof effect and usability of a handle is provided in animpact tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view showing an entire structure of a hammer drillaccording to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an internal structure of the hammerdrill.

FIG. 3 is an external view showing an outer housing and a handgripconnected to the outer housing of the hammer drill.

FIG. 4 shows a rear housing part of the outer housing which is split ina longitudinal direction, as viewed from the front (the hammer bitside).

FIG. 5 is a sectional view taken along line A-A in FIG. 2.

FIG. 6 is a sectional view taken along line B-B in FIG. 2.

FIG. 7 is a sectional view taken along line C-C in FIG. 2.

FIG. 8 is a sectional view taken along line D-D in FIG. 5.

FIG. 9 is a sectional view taken along line E-E in FIG. 5.

FIG. 10 is a sectional view taken along line F-F in FIG. 2.

FIG. 11 is a sectional view showing an entire structure of a hammerdrill according to a second embodiment of the present invention.

FIG. 12 is a sectional view taken along line G-G in FIG. 11.

FIG. 13 is a sectional view taken along line H-H in FIG. 11.

FIG. 14 is a sectional view taken along line I-I in FIG. 11.

FIG. 15 is a sectional view showing an entire structure of a hammerdrill according to a third embodiment of the present invention.

FIG. 16 is a planar view illustrating a bottom plate of a crank housingand a vibration-proofing structure which is provided for the outerhousing on the bottom plate.

FIG. 17 is a side view of FIG. 16.

FIG. 18 is a bottom view of FIG. 16.

FIG. 19 is a sectional view taken along line in FIG. 17.

REPRESENTATIVE EMBODIMENT OF THE INVENTION First Embodiment of theInvention

A first embodiment of the present invention is now described withreference to FIGS. 1 to 10. This embodiment corresponds to the featuresas defined in claims 1 to 4. In this embodiment, an electric hammerdrill is explained as a representative example of an impact tool. Asshown in FIGS. 1 and 2, a hammer drill 101 according to this embodimentmainly includes an outer housing 102 that forms an outer shell of thehammer drill 101, a body 103 that is covered by the outer housing 102, ahammer bit 119 that is detachably coupled to a front end region (on theleft as viewed in the drawings) of the body 103 via a hollow tool holder137, and a handgrip 109 that is connected to the outer housing 102 onthe side opposite from the hammer bit 119 and designed to be held by auser. The hammer bit 119 is held by the tool holder 137 such that it isallowed to linearly move with respect to the tool holder in its axialdirection. The outer housing 102, the body 103, the hammer bit 119 andthe handgrip 109 are features that correspond to the “outer shellhousing”, the “tool body”, the “tool bit” and the “handle”,respectively, according to the present invention. Further, for the sakeof convenience of explanation, the side of the hammer bit 119 is takenas the front and the side of the handgrip 109 as the rear.

As shown in FIG. 2, the body 103 includes a motor housing 105 thathouses a driving motor 111, and a crank housing 107 including a barrel106 that houses a motion converting mechanism 113, a striking mechanism115 and a power transmitting mechanism 117. The driving motor 111 isdisposed such that its rotation axis runs in a vertical direction(vertically as viewed in FIG. 3) substantially perpendicular to alongitudinal direction of the body 103 (an axial direction of the hammerbit 119). The motion converting mechanism 113 appropriately convertstorque of the driving motor 111 into linear motion and then transmits itto the striking mechanism 115. Then an impact force is generated in theaxial direction of the hammer bit 119 (the horizontal direction asviewed in FIG. 1) via the striking mechanism 115. The motion convertingmechanism 113 and the striking mechanism 115 are features thatcorrespond to the “striking mechanism part” according to this invention.Further, the power transmitting mechanism 117 appropriately reduces thespeed of torque of the driving motor 111 and transmits it to the hammerbit 119 via the tool holder 137, so that the hammer bit 119 is caused torotate in its circumferential direction. The driving motor 111 is drivenwhen a user depresses a trigger 109 a disposed on the handgrip 109.

The motion converting mechanism 113 mainly includes a crank mechanism.The crank mechanism includes a driving element in the form of a piston135 which forms a final movable member of the crank mechanism. When thecrank mechanism is rotationally driven by the driving motor 111, thepiston 135 is caused to linearly move in the axial direction of thehammer bit within a cylinder 141. The power transmitting mechanism 117mainly includes a gear speed reducing mechanism having a plurality ofgears and transmits torque of the driving motor 111 to the tool holder137. Thus, the tool holder 137 is caused to rotate in a vertical planeand then the hammer bit 119 held by the tool holder 137 is also causedto rotate. Further, the constructions of the motion converting mechanism113 and the power transmitting mechanism 117 are well known in the artand therefore their detailed description is omitted.

The striking mechanism 115 mainly includes a striking element in theform of a striker 143 that is slidably disposed within the bore of thecylinder 141 together with the piston 135, and an intermediate elementin the form of an impact bolt 145 that is slidably disposed within thetool holder 137. The striker 143 is driven via air spring action(pressure fluctuations) of an air chamber 141 a of the cylinder 141 bysliding movement of the piston 135. The striker 143 then collides with(strikes) the impact bolt 145. As a result, a striking force caused bythe collision is transmitted to the hammer bit 119 via the impact bolt145.

An operation mode switching dial 147 is mounted on a top cover 107 a ofthe crank housing 107 and can be appropriately operated by a user inorder to switch the hammer drill 101 between hammer mode and hammerdrill mode. In hammer mode, an operation is performed on a workpiece byapplying only a striking force to the hammer bit 119 in the axialdirection, and in hammer drill mode, an operation is performed on aworkpiece by applying a striking force in the axial direction and arotating force in the circumferential direction to the hammer bit 119.The operation mode switching between hammer mode and hammer drill modeis a known technique and not directly related to the present invention,and therefore their detailed description is omitted.

In the hammer drill 101 constructed as described above, when the drivingmotor 111 is driven, the rotating output of the motor is converted intolinear motion via the motion converting mechanism 113 and then causesthe hammer bit 119 to perform linear movement or striking movement inthe axial direction via the striking mechanism 115. Further, in additionto the above-described striking movement, rotation is transmitted to thehammer bit 119 via the power transmitting mechanism 117 which is drivenby the rotating output of the driving motor 111. Thus, the hammer bit119 is caused to rotate in the circumferential direction. Specifically,during operation in hammer drill mode, the hammer bit 119 performsstriking movement in the axial direction and rotation in thecircumferential direction, so that a hammer drill operation is performedon the workpiece. During operation in hammer mode, torque transmissionof the power transmitting mechanism 117 is interrupted by a clutch.Therefore, the hammer bit 119 is caused to perform only strikingmovement in the axial direction, so that a hammering operation isperformed on the workpiece.

During the above-described hammering or hammer drill operation, in thebody 103, not only impulsive and cyclic vibration is caused in the axialdirection of the hammer bit 119, but also vibration is caused in adirection transverse to the axial direction. Now, a vibration-proofingstructure is explained which serves to prevent or reduce transmission ofvibration from the body 103 to the handgrip 109 designed to be held by auser.

FIG. 3 shows the outer housing 102 that covers the body 103, and thehandgrip 109 mounted to the outer housing 102. As clearly seen from acomparison between FIG. 3 and FIG. 1, the outer housing 102 covers aregion of the body 103 other than the motor housing 105. Further,naturally, parts to be operated by a user, and more specifically, achuck 149 which is disposed in a front end region of the tool holder 137in order to detachably mount the hammer bit 119 to the tool holder 137,and the operation mode switching dial 147, are exposed from the outerhousing 102.

The outer housing 102 is generally L-shaped as viewed from the side andhas a generally cylindrical front part 102F extending substantiallyhorizontally in the axial direction of the hammer bit 119 and an oblongrear part 102R extending downward from a rear end of the front part102F. The outer housing 102 is split into two parts, or the front part102F and the rear part 102R, in the axial direction of the hammer bit119. A parting line (mating face) is shown and designated by L in FIG.3. In the following description, the front part 102F is referred to as afront housing part and the rear part 102R as a rear housing part. Inorder to assemble the front and rear housing parts 102F, 102R together,mating faces L (a rear surface of the front housing part 102F and afront surface of the rear housing part 102R) are butted with each other,and in this state, a plurality of front and rear connecting bosses 151a, 151 b formed on the outer peripheries of the front and rear housingparts are clamped and connected together by screws 151. The front andrear housing parts 102F, 102R are features that correspond to the“plurality of split elements” according to this invention.

The outer housing 102 constructed as described above is connected to thebody 103 via vibration-proofing first to fourth elastic rubbers 153,155, 157, 159 and can move with respect to the body 103 in the axialdirection of the hammer bit 119 and in a vertical direction and alateral direction which are transverse to the axial direction. In otherwords, the outer housing 102 is supported via the first to fourthelastic rubbers 153, 155, 157, 159 in no contact with an outer surfaceof the body 103 (in a floating state). The elastic rubbers 153, 155,157, 159 are now explained below.

As for the first elastic rubber 153, as shown in FIGS. 4 and 5, a totalof four upper and lower, right and left elastic rubbers are disposedbetween an upper portion of the front surface of the rear housing part102R and an upper portion of the rear end surface of the crank housing107, on the upper and lower, right and left sides with respect to theaxis of the hammer bit 119. Each of the first elastic rubbers 153 has acylindrical form, and is housed and held in a generally cylindrical part161 formed on the rear housing part 102R. Further, a front surface ofthe first elastic rubber 153 is held in surface contact with an upperportion of the rear end surface of the crank housing 107. Thus, byfrictional force between the contact surfaces, the first elastic rubber153 is prevented from moving with respect to the crank housing 107.

As shown in FIGS. 4 and 6, a total of two right and left second elasticrubbers 155 are disposed between a lower portion of the front surface ofthe rear housing part 102R and a lower portion of the rear surface ofthe motor housing 105, on the right and left sides of a vertical lineperpendicular to the axis of the hammer bit 119. Each of the secondelastic rubbers 155 has a cylindrical form, and is housed and held in agenerally cylindrical part 163 formed in the rear housing part 102R. Afront surface of the second elastic rubber 155 is held in surfacecontact with a rear end surface of a pin-like protrusion 105 a of themotor housing 105 which is loosely fitted into the cylindrical part 163.Thus, by frictional force between the contact surfaces, the secondelastic rubber 155 is prevented from moving with respect to the motorhousing 105.

As shown in FIGS. 5 and 7, a total of four upper and lower, right andleft third elastic rubbers 157 are disposed between a rear surface of aradial wall surface of the front housing part 102F and a head of a screw152 which connects a front part and a rear part of the barrel 106, onthe upper and lower, right and left sides with respect to the axis ofthe hammer bit 119. Each of the third elastic rubbers 157 has acylindrical form, and is housed and held in a generally cylindrical part165 formed on the front housing part 102F. Further, a rear surface ofthe third elastic rubber 157 is held in surface contact with the head ofthe screw 152. Thus, by frictional force between the contact surfaces,the third elastic rubber 157 is prevented from moving with respect tothe barrel 106.

In order to assemble the split front and rear housing parts 102F, 102Rinto the outer housing 102, the front housing part 102F is fitted ontothe barrel 106 from the front, and the rear housing part 102R is fittedonto the crank housing 107 and the motor housing 105 from the rear, sothat the housing parts 102F, 102R are opposed to each other, and in thisstate, the screws 151 are threadably inserted into the connecting bosses151 a, 151 b of the housing parts 102F, 102R and tightened. At thistime, the above-described first to third elastic rubbers 153, 155, 157are pressed against the crank housing 107, the motor housing 105 and thebarrel 106 in the axial direction of the hammer bit 119 (the matingdirection of the outer housing 102). Specifically, when the outerhousing 102 is mounted to the body 103, the first to third elasticrubbers 153, 155, 157 are elastically held between the outer housing 102and the body 103. In this case, the first to third elastic rubbers 153,155, 157 are held by the associated cylindrical parts 161, 163, 165formed on the outer housing 102, which facilitates mounting of the firstto third elastic rubbers 153, 155, 157.

The above-described first to third elastic rubbers 153, 155, 157 serveto reduce transmission of vibration from the body 103 to the outerhousing 102 in the vertical direction and the lateral directiontransverse to the axial direction of the hammer bit 119. The first tothird elastic rubbers 153, 155, 157 are features that correspond to the“first elastic element” according to this invention.

The hammer drill 101 according to this embodiment has a dynamicvibration reducer 171 for reducing vibration which is caused in the body103 in the axial direction of the hammer bit 119, and the fourth elasticrubber 159 is mounted to the dynamic vibration reducer 171. As shown inFIG. 5, the dynamic vibration reducer 171 mainly includes an elongatehollow dynamic vibration reducer body in the form of a cylindricalelement 172, a weight 173 disposed within the cylindrical element 172and elastic elements in the form of biasing springs 174 which aredisposed on the front and rear sides of the weight 173 in itslongitudinal direction in order to connect the weight 173 and thecylindrical element 172. The dynamic vibration reducers 171 thusconstructed are disposed on the right and left side surfaces of thecrank housing 107 in the body 103 on the opposite sides of the axis ofthe hammer bit 119, and mounted parallel to each other such that theweight 173 moves in the axial direction of the hammer bit 119. Thedynamic vibration reducer 171 forms a vibration reducing mechanism inwhich the weight 173 connected to the cylindrical element 172 via thebiasing springs 174 moves opposite to the direction of vibration whichis caused in the body 103 in the axial direction of the hammer bit 119,so that vibration of the body 103 is reduced.

The fourth elastic rubber 159 has a ring-like form, and as shown inFIGS. 5, 8 and 9, a total of four elastic rubbers 159 are provided andfitted onto the front and rear of the cylindrical element 172 of each ofthe right and left dynamic vibration reducers 171. An arcuate engagementpart 167 is formed in a region of an inner surface of each of the frontand rear housing parts 102F, 102R of the outer housing 102 which faces aside region of the fourth elastic rubber 159, and the side surface ofthe fourth elastic rubber 159 is elastically engaged with the engagementpart 167 in surface contact. With such a construction, the fourthelastic rubber 159 serves to reduce transmission of vibration from thebody 103 to the outer housing 102 in the vertical direction and thelateral direction which are transverse to the axis of the hammer bit119. The fourth elastic rubber 159 is a feature that corresponds to the“first elastic element” according to this invention.

As shown in FIG. 2, a sleeve 131 is disposed between an inner surface ofthe front housing part 102F of the outer housing 102 and an outersurface of the barrel 106. The sleeve 131 is held in surface contactwith an inner circumferential surface of the front housing part 102F andelastically held in contact with an outer circumferential surface of thebarrel 106 via two front and rear O-rings 133. The O-ring 133 is made ofrubber and serves to position the outer housing 102 in its radialdirection (in a direction transverse to the axial direction of thehammer bit 119) with respect to the barrel 106. Further, the O-ring 133elastically deforms in the radial direction so that the outer housing102 is allowed to move with respect to the barrel 106. Thus, the O-ring133 also serves as a vibration-proofing member. The O-ring 133 is afeature that corresponds to the “first elastic element” according tothis invention.

As shown in FIGS. 1 to 3, the handgrip 109 is generally D-shaped asviewed from the side and has a grip region 109A extending in thevertical direction transverse to the axial direction of the hammer bit119, and connecting regions 109B, 109C extending horizontally forwardfrom upper and lower ends of the grip region 109A. Further, front endsof the upper and lower connecting regions 109B, 109C are connected to arear end of the rear housing part 102R of the outer housing 102. Thelower connecting region 109C of the handgrip 109 is connected to a lowerend portion of the rear housing part 102R such that it can rotate on apivot 121 in the axial direction of the hammer bit 119. The upperconnecting region 109B is connected to an upper end portion of the rearhousing part 102R via a vibration-proofing compression coil spring 123such that it can move in the axial direction of the hammer bit 119 withrespect to the rear housing part 102R.

As shown in FIG. 10, two right and left compression coil springs 123 aredisposed on the opposite sides of the axis of the hammer bit 119 suchthat they can be expanded and compressed in the axial direction of thehammer bit 119. Each of the compression coil springs 123 is elasticallydisposed between the handgrip 109 and the rear housing part 102R, andits one end is held in contact with a spring seating surface on thehandgrip 109 side and the other end is held in contact with a springseating surface on the rear housing part 102R side. The compression coilsprings 123 thus arranged serve to reduce transmission of vibration fromthe body 103 to the handgrip 109 via the outer housing 102 in the axialdirection of the hammer bit 119. The compression coil spring 123 is afeature that corresponds to the “second elastic element” and the“mechanical spring” according to this invention. Further, thecompression coil spring 123 is covered by a dustproof cover 124 disposedbetween the handgrip 109 and the rear housing part 102R.

A sliding member in the form of a columnar element 125 is formed on anupper end portion of the handgrip 109 and extends horizontally forwardthrough the compression coil spring 123. The columnar element 125 slideswithin a cylindrical member 127 which is formed as a sliding guide onthe rear surface of the rear housing part 102R, so that movement of thehandgrip 109 in the axial direction of the hammer bit with respect tothe rear housing part 102R can be stabilized. Further, a stopper bolt129 is inserted into the columnar element 125 and a head of the stopperbolt 129 comes in contact with a front surface of the cylindrical member127, so that an end of rearward movement of the handgrip 109 is defined.

In this embodiment, as described above, the outer housing 102 coveringthe body 103 is connected to the body 103 via the first to third elasticrubbers 153, 155, 157 such that it can move in the axial direction ofthe hammer bit 119 with respect to the body 103, and also connected tothe body 103 via the fourth elastic rubber 159 and the O-ring 133 suchthat it can move in a direction transverse to the axial direction of thehammer bit 119 with respect to the body 103. With such a construction,as for vibration which is caused in the body 103 by striking the hammerbit 119 and transmitted from the body 103 to the outer housing 102during hammering or hammer drill operation, vibration in the verticaland lateral directions transverse to the axial direction of the hammerbit 119 is reduced by the fourth elastic rubber 159 and vibration in theaxial direction is reduced by the first to third elastic rubbers 153,155, 157. In this manner, the outer housing 102 is made proof againstvibration in all directions, or in the axial direction of the hammer bitand in the vertical and lateral directions transverse to the axialdirection.

The handgrip 109 is connected to the outer housing 102 via thecompression coil spring 123 such that it can move in the axial directionof the hammer bit 119 with respect to the outer housing 102. Therefore,vibration in the axial direction of the hammer bit 119 which istransmitted from the outer housing 102 to the handgrip 109 is reduced bythe compression coil spring 123.

As described above, according to this embodiment, as for vibrationcaused in the body 103, vibration in the axial direction of the hammerbit 119 is mainly reduced by the compression coil spring 123 whichconnects the outer housing 102 and the handgrip 109, and vibration in adirection transverse to the axial direction is reduced by the fourthelastic rubber 159 which connects the body 103 and the outer housing102. Thus, the handgrip 109 is made proof against vibration in the axialdirection of the hammer bit 119 and in a direction transverse to theaxial direction, and further, the fourth elastic rubber 159 forpreventing vibration in a direction transverse to the axial direction isdesigned to have a relatively high spring stiffness by increasing itsspring constant. With this construction, the handgrip 109 can beprevented from wobbling in a direction transverse to the axial directionwith respect to the body 103, so that usability can be enhanced.

In this embodiment, as described above, the first to third elasticrubbers 153, 155, 157 are disposed between the outer housing 102 and thebody 103, and when the front housing part 102F and the rear housing part102R are clamped and connected together by the screws 151, the elasticrubbers are held compressed therebetween. Further, vibration of thehandgrip 109 in the axial direction of the hammer bit is mainlyprevented by the compression coil spring 123. With this construction,the first to third elastic rubbers 153, 155, 157 may be designed suchthat the elastic rubbers compressed as described above can furthercompressively deform (can prevent vibration in the axial direction), orsuch that they cannot further compressively deform (cannot preventvibration in the axial direction).

Further, in this embodiment, the body 103 has the dynamic vibrationreducer 171. Therefore, the weight 173 and the biasing spring 174 whichserve as vibration reducing elements of the dynamic vibration reducer171 cooperate to actively reduce vibration caused in the body 103 in theaxial direction of the hammer bit 119. Thus, vibration of the body 103can be prevented.

Second Embodiment of the Invention

A second embodiment of the present invention is now described withreference to FIGS. 11 to 14. The second embodiment corresponds to thefeatures as defined in claims 1 to 4. This embodiment relates to amodification to the vibration-proofing structure of the outer housing102, and more particularly to a modification to the vibration-proofingstructure for preventing vibration in a direction transverse to theaxial direction of the hammer bit 119. Structures of this embodimentother than the vibration-proofing structure, such as an entire structureof the hammer drill 101, a structure for driving the hammer bit 119, anda structure for mounting the handgrip 109, are identical to those in theabove-described first embodiment. Therefore, components which aresubstantially identical to those in the first embodiment are given likenumerals as in the first embodiment and are not described or brieflydescribed.

As shown in FIG. 12, the outer housing 102 is elastically connected tothe body 103 via the vibration-proofing first to third elastic rubbers153, 155, 157 (see FIG. 6 as to the second elastic rubber 155). Further,as shown in FIG. 11, a front end of the outer housing 102 is connectedto the barrel 106 via the sleeve 131 and the O-ring 133. As shown inFIG. 11, the lower connecting region 109C of the handgrip 109 isconnected to the lower end portion of the rear housing part 102R suchthat it can rotate on the pivot 121 in the axial direction of the hammerbit 119 and the upper connecting region 109B is connected to the upperend portion of the rear housing part 102R via the compression coilspring 123 such that it can move in the axial direction of the hammerbit 119 with respect to the rear housing part 102R. The above-describedconstruction is the same as in the first embodiment.

In this embodiment, the body 103 of the hammer drill 101 is not providedwith the dynamic vibration reducer 171 described in the firstembodiment. As shown in FIGS. 12 to 14, fifth elastic rubbers 176 aredisposed in right and left side regions of the crank housing 107 in thebody 103, and the outer housing 102 is connected to the body 103 via thefifth elastic rubber 176 such that it can move in a direction transverseto the axial direction of the hammer bit 119 with respect to the body103. The fifth elastic rubber 176 corresponds to the fourth elasticrubber 159 described in the first embodiment and is a feature thatcorresponds to the “first elastic element” according to this invention.

A total of four front and rear, right and left fifth elastic rubbers 176are disposed between right and left outer side surfaces of the crankhousing 107 and right and left inner side surfaces of the front housingpart 102F of the outer housing 102 which face each other. Each of thefifth elastic rubbers 176 is cylindrically-shaped, and housed and heldwithin a generally circular cylindrical part 177 which is formed on thecrank housing 107 and has a lateral opening. In this state, part of thefifth elastic rubber 176 protrudes from the cylindrical part 177. Theprotruding end surface of the fifth elastic rubber 176 is held insurface contact with a protrusion 178 formed on the inner side of thefront housing part 102F. Thus, by frictional force between the contactsurfaces, the fifth elastic rubber 176 is prevented from moving withrespect to the front housing part 102F.

According to this embodiment constructed as described above, the fifthelastic rubber 176 can prevent vibration of the outer housing 102 byreducing vibration caused in the body 103 in the lateral directiontransverse to the axial direction of the hammer bit 119. Further, theother effects of this embodiment are the same as the effects of thefirst embodiment.

In this embodiment, with the construction in which the fifth elasticrubber 176 is held by the cylindrical part 177 of the crank housing 107,the fifth elastic rubber 176 can be prevented from slipping off whenassembling the front housing part 102F and the rear housing part 102R,so that the assembling operation can be easily performed. The locationof the cylindrical part 177 may be changed from the crank housing 107side to the outer housing 102 side.

Third Embodiment of the Invention

A third embodiment of the present invention is now described withreference to FIGS. 15 to 18. The third embodiment corresponds to thefeatures as defined in claims 5 to 7. As shown in FIG. 15, a hammerdrill 201 according to this embodiment mainly includes an outer housing202 that forms an outer shell of the hammer drill 201, a body 203 thatis covered by the outer housing 202, a hammer bit 219 detachably coupledto a front end region (on the left as viewed in the drawings) of thebody 203 via a hollow tool holder 237, and a handgrip 209 designed to beheld by a user and connected to the outer housing 202 on the sideopposite to the hammer bit 219. The hammer bit 219 is held by the toolholder 237 such that it is allowed to linearly move with respect to thetool holder in its axial direction. The outer housing 202, the body 203,the hammer bit 219 and the handgrip 209 are features that correspond tothe “outer shell housing”, the “tool body”, the “tool bit” and the“handle”, respectively, according to the present invention. Further, forthe sake of convenience of explanation, the side of the hammer bit 219is taken as the front and the side of the handgrip 209 as the rear.

The body 203 includes a motor housing 205 that houses a driving motor211, and a crank housing 207 including a barrel 206 that houses a motionconverting mechanism, a striking mechanism and a power transmittingmechanism which are not shown. The crank housing 207 is designed suchthat its regions other than the barrel 206 are housed in the motorhousing 205, and is connected to the motor housing 205. The drivingmotor 211 is disposed such that its rotation axis runs in a verticaldirection (vertically as viewed in FIG. 15) substantially perpendicularto a longitudinal direction of the body 203 (the axial direction of thehammer bit 219).

The motion converting mechanism appropriately converts torque of thedriving motor 211 into linear motion and then transmits it to thestriking mechanism, so that the hammer bit 219 is caused to performstriking movement in its axial direction via the striking mechanism. Themotion converting mechanism and the striking mechanism are features thatcorrespond to the “striking mechanism part” according to this invention.Further, the power transmitting mechanism appropriately reduces thespeed of torque of the driving motor 211 and transmits it to the hammerbit 219 via the tool holder 237, so that the hammer bit 219 is caused torotate in its circumferential direction. Specifically, in hammer drillmode, the hammer bit 219 performs striking movement in the axialdirection and rotation in the circumferential direction so that a hammerdrill operation is performed on a workpiece. In hammering mode, torquetransmission of the power transmitting mechanism is interrupted by theclutch. Therefore, the hammer bit 219 performs only the strikingmovement in the axial direction so that a hammering operation isperformed on a workpiece. Further, the driving motor 211 is driven whena user depresses a trigger 209 a disposed on the handgrip 209.

A vibration-proofing structure for preventing or reducing transmissionof vibration from the body 203 to the handgrip 209 designed to be heldby a user during hammering or hammer drill operation is now explainedwith reference to FIGS. 15 to 19. In this embodiment, the handgrip 209and the outer housing 202 may be formed in one piece, or they may beseparately formed and integrally connected to each other. The outerhousing 202 is connected to the body 203 via a vibration-proofingcompression coil spring 281 such that it can move in the axial directionof the hammer bit 219 with respect to the body 203, and also connectedto the body 203 via a plurality of vibration-proofing rubber rings 283such that it can move in the vertical and lateral directions transverseto the axial direction of the hammer bit 219 with respect to the body203. The rubber rings 283 and the compression coil spring 281 arefeatures that correspond to the “first elastic element” and the “secondelastic element”, respectively, according to this invention.

The handgrip 209 is generally D-shaped as viewed from the side and has agrip region 209A extending in the vertical direction transverse to theaxial direction of the hammer bit 219, and connecting regions 209B, 209Cextending substantially horizontally forward from upper and lower endsof the grip region 209A. Further, front ends of the upper and lowerconnecting regions 209B, 209C are integrally connected to a rear end ofthe outer housing 202. As shown in FIG. 15, the compression coil spring281 is elastically disposed between a front surface of an upper endportion of the outer housing 202 to which the handgrip 209 a isconnected, and a rear surface of a rear upper end portion of the crankhousing 207 in the body 203. In this state, the compression coil spring281 can be expanded and compressed in the axial direction of the hammerbit 119. One end of the compression coil spring 281 is held in contactwith a spring receiving part 202 a on the outer housing 202 and theother end is held in contact with a spring receiving part 207 a on thecrank housing 207. The compression coil spring 281 thus arranged servesto reduce transmission of vibration from the body 203 to the handgrip209 in the axial direction of the hammer bit 219.

The compression coil spring 281 exerts a forward biasing force on thecrank housing 207, and thus the handgrip 209 and the outer housing 202are subjected to a relatively rearward biasing force. Therefore, asshown in FIG. 15, a stopper ring 282 made of rubber or resin is disposedbetween an outer front surface 205 a of the motor housing 205 in thebody 203 and a stepped surface 202 b formed on the inner surface of theouter housing 202 in the radial direction and facing the outer frontsurface 205 a. With this construction, an initial positional relationbetween the outer housing 202 and the body 203 is defined.

As shown in FIGS. 16 to 19, the rubber rings 283 are fitted onto bothaxial ends of each of elongate pin members 284 and retained viarespective rubber ring retainers 285. The pin member 284 is a featurethat corresponds to the “rod-like member” according to this invention.Two right and left elongate cylindrical members 286 are disposed on theunderside (outer surface) of a bottom plate 207 b of the crank housing207 on the opposite sides of the axis of the hammer bit 219 and extendparallel to each other in the axial direction of the hammer bit 219. Theright and left cylindrical members 286 may be integrally formed with orfixedly mounted to the crank housing 207. Each of the pin members 284extends through the associated cylindrical member 286, and as shown inFIG. 19, the pin member 284 is supported at the both ends of thecylindrical member 286 via sliding bearings 287 such that it can slidein the axial direction of the hammer bit 219 with respect to thecylindrical member 286. The both axial ends of the pin member 284protrude from the cylindrical member 286 to the outside, and the rubberrings 283 are coaxially mounted onto the protruding ends of the pinmember 284 via the rubber ring retainers 285. Thus, a total of fourfront and rear, right and left rubber rings 283 are disposed in a lowerregion outside the crank housing 207.

As shown in FIG. 15, four cylindrical holding parts 288 are formed inthe outer housing 202 and house and hold the four rubber rings 283. Eachof the rubber rings 283 is held in surface contact with an innercircumferential surface of the cylindrical holding part 288 andconnected to the cylindrical holding part 288 such that it canelastically deform in the radial direction. In this manner, the outerhousing 202 is connected to the body 203 via the four rubber rings 283disposed side by side substantially on the same horizontal plane, in thevicinity of the bottom of the crank housing 207 or substantially in amiddle region of the body 203 in the vertical direction, such that itcan move in a direction (vertical and lateral directions) transverse tothe axial direction of the hammer bit 219 with respect to the body 203.

Further, both axial end surfaces of the pin member 284 (end surfaces ofthe rubber ring retainers 285) are held in contact with the bottom ofthe cylindrical holding part 288. Therefore, the outer housing 202 andthe pin member 284 are prevented from moving in the axial direction ofthe hammer bit 219 with respect to each other and thus form anintegrated structure. Therefore, the pin member 284 moves in the axialdirection of the hammer bit 219 together with the outer housing 202 withrespect to the crank housing 207 and serves as a guide rail for guidingthe movement of the outer housing 202.

As shown in FIG. 16, an opening 286 a is formed in a region of an uppersurface of the cylindrical member 286 which faces an inner surface ofthe bottom plate 207 b of the crank housing 207 (the inside of thehousing), and lubricant (grease) within the crank housing 207 is ledinto the cylindrical member 286 through the opening 286 a. Thus, asliding surface between the pin member 284 and the cylindrical member286 (the sliding bearing 287) is lubricated with lubricant, so thatsmoothness of their sliding movement and their durability can beimproved. Further, an oil seal 289 for preventing leakage of lubricantis provided on the outer side of the sliding bearing 287.

As shown in FIG. 15, like in the first embodiment, the outer housing 202for covering the body 203 covers a region of the body 203 other than alower region of the motor housing 205. Further, parts to be operated bya user, and more specifically, a chuck 249 which is disposed in a frontend region of the tool holder 237 in order to removably attach thehammer bit 219 to the tool holder 237, and an operation mode switchingdial 247 for switching the operation mode of the hammer bit 219, areexposed from the outer housing 202.

A dynamic vibration reducer 271 is mounted on each of the right and leftside surfaces of the crank housing 207. Although not shown, the dynamicvibration reducer 271 has the same construction as the dynamic vibrationreducer 171 which is described in the first embodiment. The dynamicvibration reducer 271 forms a vibration reducing mechanism in which theweight connected to the cylindrical element via an elastic element inthe form of the biasing spring moves opposite to the direction ofvibration which is caused in the body 203 in the axial direction of thehammer bit 219, so that vibration of the body 203 is reduced.

In this embodiment, as described above, the outer housing 202 coveringthe body 203 is integrally formed with the handgrip 209. Further, theouter housing 202 is connected to the body 203 via the compression coilspring 281 such that it can move in the axial direction of the hammerbit 219 with respect to the body 203, and also connected to the body 203via the rubber ring 283 such that it can move in the vertical andlateral directions transverse to the axial direction of the hammer bit219 with respect to the body 203. With such a construction, as forvibration which is caused in the body 203 by striking the hammer bit 219and transmitted to the outer housing 202 during hammering or hammerdrill operation, vibration in the axial direction of the hammer bit 219is reduced by the compression coil spring 281 and vibration in thevertical and lateral directions transverse to the axial direction of thehammer bit 219 is reduced by the rubber rings 283. In this manner, theouter housing 202 and the handgrip 209 are made proof against vibrationin all directions, or in the axial direction of the hammer bit 219 andin the vertical and lateral directions transverse to the axial directionof the hammer bit.

Specifically, according to this embodiment, like in the above-describedfirst embodiment, the handgrip 209 to be held by a user is made proofagainst vibration in the axial direction of the hammer bit 209 and in adirection transverse to the axial direction, and the rubber ring 283 forpreventing vibration in a direction transverse to the axial direction isdesigned to have a relatively high spring stiffness by increasing itsspring constant. With this construction, the handgrip 209 is preventedfrom wobbling in a direction transverse to the axial direction withrespect to the body 203, so that usability can be enhanced.

Further, the rubber ring 283 in this embodiment may be designed toprevent vibration not only in a direction transverse to the axialdirection of the hammer bit 219 but also in the axial direction of thehammer bit.

Further, in this embodiment, the pin member 284 is provided on the crankhousing 207 and slidably extends through the cylindrical member 286 inthe axial direction of the hammer bit 219, and the outer housing 202moves together with the pin member 284 in the axial direction of thehammer bit 219 with respect to the crank housing 207. Specifically, thepin member 284 serves as a guide rail for guiding the movement of theouter housing 202 with respect to the crank housing 207. Thus, the outerhousing 202 can move with respect to the crank housing 207 withstability, so that usability of the impact tool can be improved.Further, with the construction in which lubricant within the crankhousing 207 is supplied to the sliding surface between the pin member284 and the cylindrical member 286, smoothness and durability of thesliding parts can be effectively enhanced.

In the first to third embodiments, the hammer drills 101, 201 areexplained as representative examples of the impact tool, but thisinvention can also be applied to a hammer in which the hammer bits 119,219 perform only striking movement.

In view of the above-described invention, the following aspects can beprovided.

Aspect 1

“The impact tool as defined in any one of claims 2 to 4, comprising aplurality of the first elastic elements which are disposed symmetricallywith respect to an axis of the tool bit.”

Aspect 2

“The impact tool as defined in claim 3, wherein the first elasticelement is held by a cylindrical part formed on at least one of the toolbody and the outer shell housing when the split elements are connectedto each other.”

Aspect 3

“The impact tool as defined in claim 8, wherein the dynamic vibrationreducer has a columnar element, a weight which is housed within thecylindrical element and can linearly move in an axial direction of thetool bit, and an elastic element which connects the weight and thecylindrical element, and

the first elastic element is disposed on an outer circumferentialsurface of the cylindrical element and elastically held in contact withan inner surface of the outer shell housing.”

Aspect 4

“The impact tool as defined in any one of claims 5 to 7, wherein aplurality of the first elastic elements are disposed side by side on onehorizontal plane, in a middle region of the tool body in a verticaldirection transverse to the axial direction of the tool bit.”

Aspect 5

“The impact tool as defined in claim 6 or 7, wherein lubricant in thetool body is supplied to a sliding part between the rod-like member andthe tool body.”

DESCRIPTION OF NUMERALS

-   101 hammer drill (impact tool)-   102 outer housing (outer shell housing)-   102F front housing part (split element)-   102R rear housing part (split element)-   103 body (tool body)-   105 motor housing-   105 a pin-like protrusion-   106 barrel-   107 crank housing-   107 a top cover-   109 handgrip (handle)-   109A grip region-   109B upper connecting region-   109C lower connecting region-   109 a trigger-   111 driving motor (motor)-   113 motion converting mechanism (striking mechanism part)-   115 striking mechanism (striking mechanism part)-   117 power transmitting mechanism-   119 hammer bit (tool bit)-   121 pivot-   123 compression coil spring (second elastic element)-   124 dustproof cover-   125 columnar element-   127 cylindrical member-   129 stopper bolt-   131 sleeve-   133 O-ring (first elastic element)-   135 piston-   137 tool holder-   141 cylinder-   141 a air chamber-   143 striker-   145 impact bolt-   147 operation mode switching dial-   149 chuck-   151 screw-   151 a front connecting boss-   151 b rear connecting boss-   152 screw-   153 first elastic rubber (first elastic member)-   155 second elastic rubber (first elastic member)-   157 third elastic rubber (first elastic member)-   159 fourth elastic rubber (first elastic member)-   161 cylindrical part-   163 cylindrical part-   165 cylindrical part-   167 engagement part-   171 dynamic vibration reducer-   172 cylindrical element-   173 weight-   174 biasing spring-   176 fifth elastic rubber (first elastic member)-   177 cylindrical part-   178 protrusion-   201 hammer drill (impact tool)-   202 outer housing (outer shell housing)-   202 a spring receiving part-   202 b stepped surface-   203 body-   205 motor housing-   205 a outer front surface-   206 barrel-   207 crank housing-   207 a spring receiving part-   207 b bottom plate-   209 handgrip (handle)-   209A grip region-   209B upper connecting region-   209C lower connecting region-   209 a trigger-   211 driving motor-   219 hammer bit (tool bit)-   237 tool holder-   247 operation mode switching dial-   249 chuck-   281 compression coil spring (second elastic element)-   282 stopper ring-   283 rubber ring (first elastic element)-   284 pin member (rod-like member)-   285 rubber retainer-   286 cylindrical member-   286 a opening-   287 sliding bearing-   288 cylindrical holding part-   289 oil seal

The invention claimed is:
 1. An impact tool which linearly drives a toolbit in an axial direction of the tool bit to cause the tool bit toperform a predetermined hammering operation, comprising: a motor, astriking mechanism part that is driven by the motor and causes the toolbit to linearly move, a tool body that houses the motor and the strikingmechanism part, an outer shell housing that covers at least part of thetool body, a first elastic element that elastically connects the outershell housing to the tool body such that the outer shell housing canmove in a direction transverse to the axial direction of the tool bitwith respect to the tool body, a handle designed to be held by a user, asecond elastic element that connects the handle to the outer shellhousing such that the handle can move in the axial direction of the toolbit with respect to the tool body, wherein the tool body has a barrelextending in the axial direction of the tool bit, the first elasticelement is interveningly disposed between an outer circumferentialsurface of the barrel and an inner circumferential surface of the outershell housing which covers the barrel, and the first elastic elementpositions the outer shell housing in a radial direction with respect tothe tool body, and wherein the striking mechanism comprises a motionconverting element and a striking element, the striking element is atleast partly housed by the barrel of the tool body, a plurality of thirdelastic elements that can elastically deform in the direction transverseto the axial direction of the tool bit, and a rod-like member which isprovided in the tool body and slidably extends through the tool body inthe axial direction of the tool bit, wherein: the outer shell housing isconnected to the tool body via at least the plurality of third elasticelements and the second elastic element, the rod-like member serves as aguide rail for guiding movement of the outer shell housing in the axialdirection of the tool bit with respect to the tool body, the rod-likemember extends in the axial direction of the tool bit and an elasticelement of the plurality of third elastic elements is mounted to eachend of the rod-like member, and the tool body comprises a first holethat is disposed close to the tool bit and a second hole that isdisposed remote from the tool bit in the axial direction of the toolbit, and the rod-like member is provided to penetrate the first andsecond holes.
 2. The impact tool as defined in claim 1, wherein thehandle has a grip region extending in a direction transverse to theaxial direction of the tool bit and one end of the grip region in anextending direction is connected to the outer shell housing by thesecond elastic element comprising a mechanical spring.
 3. The impacttool as defined in claim 1, wherein the outer shell housing is splitinto a plurality of split elements in the axial direction of the toolbit and formed by connecting the split elements to each other.
 4. Theimpact tool as defined in claim 1, comprising a dynamic vibrationreducer which is provided in the tool body and reduces vibration of thetool body in the axial direction of the tool bit.
 5. An impact tool,which linearly drives a tool bit in an axial direction of the tool bitto cause the tool bit to perform a predetermined hammering operation,comprising: a motor, a striking mechanism part that is driven by themotor and causes the tool bit to linearly move, a tool body that housesthe motor and the striking mechanism part, an outer shell housing thatcovers at least part of the tool body, a handle that is designed to beheld by a user and integrally formed on an opposite side of the outershell housing from the tool bit, a plurality of first elastic elementsthat can elastically deform in a direction transverse to the axialdirection of the tool bit, a second elastic element that can elasticallydeform in the axial direction of the tool bit, and a rod-like memberwhich is provided in the tool body and slidably extends through the toolbody in the axial direction of the tool bit, wherein: the outer shellhousing is connected to the tool body via at least the plurality offirst elastic elements and the second elastic element, the rod-likemember serves as a guide rail for guiding movement of the outer shellhousing in the axial direction of the tool bit with respect to the toolbody, the rod-like member extends in the axial direction of the tool bitand a first elastic element of the plurality of first elastic elementsis mounted to each end of the rod-like member, and the tool bodycomprises a first hole that is disposed close to the tool bit and asecond hole that is disposed remote from the tool bit in the axialdirection of the tool bit, and the rod-like member is provided topenetrate the first and second holes.
 6. The impact tool as defined inclaim 5, wherein the rod-like member and the outer shell housing areconnected to each other via the plurality of first elastic elements. 7.The impact tool as defined in claim 5, comprising a dynamic vibrationreducer which is provided in the tool body and reduces vibration of thetool body in the axial direction of the tool bit.
 8. The impact tool asdefined in claim 5, wherein the striking mechanism comprises a motionconverting element and a striking element, and the striking element isat least partly housed by the tool body.
 9. An impact tool, whichlinearly drives a tool bit in an axial direction of the tool bit tocause the tool bit to perform a predetermined hammering operation,comprising: a motor, a striking mechanism part that is driven by themotor and causes the tool bit to linearly move, a tool body that housesthe motor and the striking mechanism part, an outer shell housing thatcovers at least part of the tool body, a handle that is designed to beheld by a user and integrally formed on an opposite side of the outershell housing from the tool bit, a plurality of first elastic elementsthat can elastically deform in a direction transverse to the axialdirection of the tool bit, a second elastic element that can elasticallydeform in the axial direction of the tool bit, and a rod-like memberwhich is provided in the tool body and slidably extends through the toolbody in the axial direction of the tool bit, wherein: the outer shellhousing is connected to the tool body via at least the plurality offirst elastic elements and the second elastic element, the rod-likemember serves as a guide rail for guiding movement of the outer shellhousing in the axial direction of the tool bit with respect to the toolbody, the rod-like member extends in the axial direction of the tool bitand a first elastic element of the plurality of first elastic elementsis mounted to each end of the rod-like member, and the rod-like memberis provided with two elongate members, and the two elongate members aredisposed on opposite sides of the axis of the tool bit to each other.